After seeing that tanks with riveted construction were vulnerable it was decided to produce a welded tank.
In September 1936, during maneuvers in Byelorussia, British General Wavell and Colonel Martel saw the tank. Martel wrote: "The design of the fighting body is not very good but the performance of the machine is at least twice as good as the A9." He further suggested that the British War Office purchase one.
Had new Saslavsky brakes, new main clutch, new turret, thicker armor, and all welded.
The main gun was the 45 mm model 1934 / 45 mm Model 35 tank gun.
In 1938 an improved gun sighting system, called TOS, was installed. This was developed by V. A. Pavlov and A. Z. Tumanov. The main armament could now better fire on the move.
The engine was a copy of a German BMW aircraft engine.
New engine with an improved gearbox with 3 forward gears. Used a control stick for steering.
The first turrets for the BT-7 were the same cylindrical turret that was used on the BT-5. A conical turret was then used with MG in rear. It had round hatches on top which led to the nickname "Mickey Mouse" from German troops.